I wired this button up in both illuminated and non illuminated mores, with and without chassis (battery) ground. At first the button is dim as expected. After I use the button once then turn it off, it stays lit and it doesn't cut power. I don't understand how or why, but there are no instructions and I'm not an electrical engineer. I'm just a guy with a multimeter that wants to put a switch in place of the 2005 Subaru "test connectors" that simple complete a 12v circuit to let the ECU know it's in test mode. With this button engaged, the car still didn't detect a connection. The diagram provided on this page doesn't seem to apply to cars I guess?